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* SUPPORT, LICENSE: New files. * Numerous files touched as part of merging the 4.5 branch onto the mainline development trunk and ensuring that the script that cuts snapshots and releases works on the documentation.
40 lines
1.4 KiB
Perl
40 lines
1.4 KiB
Perl
@c
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@c COPYRIGHT (c) 1988-2002.
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@c On-Line Applications Research Corporation (OAR).
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@c All rights reserved.
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@c
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@c $Id$
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@c
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@chapter Memory Model
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@section Introduction
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A processor may support any combination of memory
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models ranging from pure physical addressing to complex demand
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paged virtual memory systems. RTEMS supports a flat memory
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model which ranges contiguously over the processor's allowable
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address space. RTEMS does not support segmentation or virtual
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memory of any kind. The appropriate memory model for RTEMS
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provided by the targeted processor and related characteristics
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of that model are described in this chapter.
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@section Flat Memory Model
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The MC68xxx family supports a flat 32-bit address
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space with addresses ranging from 0x00000000 to 0xFFFFFFFF (4
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gigabytes). Each address is represented by a 32-bit value and
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is byte addressable. The address may be used to reference a
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single byte, word (2-bytes), or long word (4 bytes). Memory
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accesses within this address space are performed in big endian
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fashion by the processors in this family.
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Some of the MC68xxx family members such as the
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MC68020, MC68030, and MC68040 support virtual memory and
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segmentation. The MC68020 requires external hardware support
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such as the MC68851 Paged Memory Management Unit coprocessor
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which is typically used to perform address translations for
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these systems. RTEMS does not support virtual memory or
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segmentation on any of the MC68xxx family members.
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